1. Field of the Invention
This invention relates to the field of treating pulp/paper streams for removing colorants therefrom. The invention further relates to means for removing dioxins and aromatic organic halogens, especially chlorinated phenols, from aqueous solutions.
2. Technology Review
Several principal means for making pulp and paper from wood products are set forth in chapter 33 of Shreve's Chemical Process Industries, 5th ed., the disclosure of which is fully incorporated by reference herein. One well-known means is known as the kraft process. This process involves several stages, some of which are acidic and others which are caustic in nature. Many of the solutions in contact with wood during this process break down lignins into solubilized products which add color to the water stream and intermediate paper products. Often, these intermediate products are subjected to intense bleaching phases to produce an end product with improved whiteness. Bleaching may also be done in the sulfite process, or in mechanical pulping to a lesser extent.
The presence of known colorants, dioxins and adsorbable organic halogens (or AOX's), especially chlorinated phenols, makes pulp/paper waste waters, particularly bleach effluents, unsuitable for discharge. Current technologies for treating such waters include organic oxidation using ultraviolet light, a rather costly technique, and various biotreatments which are not always effective. Still other known means include dumping mass quantities of lime or alum into effluent streams, the latter of which causes complications by generating significant amounts of spent solid contaminants.